Department of Chemistry and Life Science, Bioscience Institute, Sahmyook University, Seoul, 01795, Republic of Korea.
Genes Genomics. 2021 Mar;43(3):237-249. doi: 10.1007/s13258-021-01051-w. Epub 2021 Mar 3.
DNA tandem repeats (TRs) are often abundant and occupy discrete regions in eukaryotic genomes. These TRs often cause or generate chromosomal rearrangements, which, in turn, drive chromosome evolution and speciation. Tracing the chromosomal distribution of TRs could therefore provide insights into the chromosome dynamics and speciation among closely related taxa. The basic chromosome number in the genus Senna is 2n = 28, but dysploid species like Senna tora have also been observed.
To understand the dynamics of these TRs and their impact on S. tora dysploidization.
We performed a comparative fluorescence in situ hybridization (FISH) analysis among nine closely related Senna species and compared the chromosomal distribution of these repeats from a cytotaxonomic perspective by using the ITS1-5.8S-ITS2 sequence to infer phylogenetic relationships.
Of the nine S. tora TRs, two did not show any FISH signal whereas seven TRs showed similar and contrasting patterns to other Senna species. StoTR01_86, which was localized in the pericentromeric regions in all S. tora, but not at the nucleolar organizer region (NOR) site, was colocalized at the NOR site in all species except in S. siamea. StoTR02_7_tel was mostly localized at chromosome termini, but some species had an interstitial telomeric repeat in a few chromosomes. StoTR05_180 was distributed in the subtelomeric region in most species and was highly amplified in the pericentromeric region in some species. StoTR06_159 was either absent or colocalized in the NOR site in some species, and StoIGS_463, which was localized at the NOR site in S. tora, was either absent or localized at the subtelomeric or pericentromeric regions in other species.
These data suggest that TRs play important roles in S. tora dysploidy and suggest the involvement of 45S rDNA intergenic spacers in "carrying" repeats during genome reshuffling.
DNA 串联重复（TR）在真核生物基因组中通常很丰富，占据离散区域。这些 TR 经常导致或产生染色体重排，进而推动染色体进化和物种形成。因此，追踪 TR 在染色体上的分布可以深入了解密切相关类群的染色体动态和物种形成。金合欢属的基本染色体数为 2n=28，但也观察到了多倍体物种，如 Senna tora。
了解这些 TR 的动态及其对 S. tora 多倍体化的影响。
我们对 9 种亲缘关系密切的 Senna 物种进行了比较荧光原位杂交（FISH）分析，并通过使用 ITS1-5.8S-ITS2 序列从细胞分类学的角度比较了这些重复序列的染色体分布，以推断系统发育关系。
在 9 种 S. tora TR 中，有 2 种没有显示任何 FISH 信号，而有 7 种 TR 显示出与其他 Senna 物种相似但又有差异的模式。StoTR01_86 定位于所有 S. tora 的着丝粒区域，但不在核仁组织区（NOR）位点，在除 S. siamea 之外的所有物种中都与 NOR 位点共定位。StoTR02_7_tel 主要定位于染色体末端，但一些物种在几条染色体上有一个内部端粒重复。StoTR05_180 在大多数物种中分布在端粒区，在一些物种中在着丝粒区高度扩增。StoTR06_159 在一些物种中要么缺失，要么与 NOR 位点共定位，而在 S. tora 中定位于 NOR 位点的 StoIGS_463 要么缺失，要么定位于端粒或着丝粒区，在其他物种中。
这些数据表明 TR 在 S. tora 多倍体化中发挥重要作用，并表明 45S rDNA 基因间区在基因组重排过程中“携带”重复序列。
